Multiplexing has been used since the days of Thomas Edison to transmit multiple signals on a limited number of wires. Because of the advances in the electronics in recent years and the increasing importance of information transmission, multiplexing schemes are widely used in many industries. For example, telephone companies multiplex multiple voice or transmission signals to transmit greater amounts of information without increasing the number of cables being used. Many jet fighters routinely use multiplexing to transmit large amounts of data from one area of the airplane to another.
The recent advances in network technology further demonstrate the importance of using multiplexing to optimize information transmission over a limited number of wires or optical cables. Most multiplexers in use today multiplex signals using time division multiplexing. In this method, time slots are divided such that each data channel occupies multiple signals, thereby allowing multiple signals to be transmitted over only one pair of wires. Although time division multiplexing enables transmission of large amounts of information in one pair of wires, the implementation of this type of multiplexing is very costly, making multiplexing too expensive for widespread use.